Chemical Science. 159 
has much greater power than one composed of the former, which 
is very feeble. The case is the same with the two sets, copper 
and zinc, and copper and bismuth. © 
2. Brass, copper, and lead, according to Bockmann, have a 
conducting power as to heat of 344, 346, and 850; nevertheless, 
acircuit of brass and copper is sensibly stronger in its action than 
a circuit of lead and copper. 
3. Finally, silver in contact with antimony is electrized nega- 
tively, in contact with zinc it is still more powerfully so; but 
- other circumstances being equal, a circuit of antimony and silver 
has seven times the power over a magnetic needle that a circle of 
zine and silver has. Antimony is positive when opposed to pla- 
tina, gold, or silver, and negative when opposed to copper, tin, 
lead, or zinc; but whichever of those metals be formed into a 
circuit with antimony, the same effect is obtained, the same pole 
of the needle always being urged to the same side. Bismuth and 
antimony are both positive when in contact with platina, gold, and 
silver, but all other things being equal, as the dimensions of the 
metal, the soldering, the temperature and arrangement, a circuit 
ormed of bismuth and one of the last named metals, turns the 
ole of the needle 14°, 51°, or 45° to the east, whilst if antimony be 
substituted for the bismuth, the pole is thrown 18°, 25°, or 30° to 
the west. 
Being induced to consider the rupture of the equilibrium of 
temperature as the principal cause of the electro-magnetic action 
of Seebeck’s circle, M. d’Yelin endeavoured to obtain similar 
effects with a single piece of metal, and having obtained very de- 
cided effects, he has given to this class of phenomena the name of 
thermo-magnetism. ‘That very feeble magnetic action might be 
observed, very delicate needles were used; they were of great 
tenuity and suspended by a single spider’s thread. 
If a band of any single metal be formed into a circuit of any 
figure, by riveting one of its ends near the other, and the projecting 
end be heated by a flame, whilst the circuit is plunged in cold 
water, this band will become electro-magnetic, and its properties 
may be easily ascertained. The experiment was made with zine, 
bismuth, brass, tin, lead, and copper, and M. d’ Yelin infers that 
“ all metallic bodies acquire electro-magnetic properties when their 
various parts are unequally heated, and that the action is stronger 
as the difference of temperature is greater.” 
This fundamental experiment being established, the following 
are the principal results obtained by the author:— 
I, The metals, in reference to their thermo-magnetic properties, 
may be ranged as follows, commencing with those which possess 
them in the highest degree, bismuth, antimony, zinc, silver, pla- 
tina, copper, brass, gold, tin, lead. 
II. A metal acts differently on the needle according as the hot or 
